The conventional one-way intravenous catheter originates from the need of infusing pharmaceutical liquids (flebochlysis) or blood (transfusion) into the venous system, and of drawing blood therefrom (donation).
An intravenous catheter assembly typically comprises a thin teflon tube (cannula), of a size which depends on the required use, attached to a plastic hub, and provided with standard connecting means for connection to the infusion or blood drawing sets. The catheter tube is inserted into the vein of a patient by means of an inner coaxial stainless steel needle, which is withdrawn by retracting it from the catheter tube right after the insertion of the catheter into the patient's vein. The needle is attached to a separate plastic support.
One-way catheters are generally employed in hospitals for administering pharmaceutical solutions directly into the venous system. The only way of the catheter is connected to an infusion set, which is in its turn connected to the container of the liquid to be infused. After that the catheter has been safely placed into the patient's vessel and once the needle is withdrawn from the catheter, the user should dispose of the needle, but very often he connects the infusion set as a first step, and he tapes the catheter on the patient's skin, and just drops the needle nearby, so that he can retreave it and dispose of it later.
The various handlings of the needle, once it has been removed, bring about considerable risk of accidental needle injury, which may have serious consequences if the needle is infected by the patient's blood. This problem is particularly critical in the hospital departments where serious infectious diseases such as hepatitis or AIDS are treated.
In order to reduce the danger coming from used needles, there have been provided plastic sheaths or caps that should be employed to cover the needle right after use, but this operation may easily cause accidental injury right when the sheath is being placed again on the needle.
A device directed to the solution of the above-mentioned problem is disclosed in the U.S. Ser. No. 335,472, filed on Apr. 10, 1989, now U.S. Pat. No. 5,000,740, assigned to a common assignee and incorporated by reference. Such patent comprises the state of the art within the meaning of Article 54 (3) and (4) EPC with respect to the present application.
The one-way catheter disclosed in the above-mentioned patent application comprises a catheter tube or cannula with the relevant hub, a needle located within said cannula and attached to a specially designed plastic housing, a protective needle guard provided with a longitudinal slot which may slide with respect to said housing so as to completely cover the needle, and a removable protective sheath which surrounds the needle and catheter tube prior to use. As initially assembled, the needle guard is completely retracted with respect to the needle housing, and the needle and catheter tube are covered by the above mentioned sheath, which is releasably connected by means of a flange to said needle guard. Prior to use, the sheath is removed and the catheter is inserted into the patient's vessel, as usual. Once the tip of the needle has reached the blood vessel, the user, while holding the device by the needle housing, advances the above mentioned tubular needle guard, thereby disengaging the catheter hub from the needle and causing the retraction of the needle within the needle guard starting from the rear end of the needle.
Thus, the immediate protection of the needle right after use is obtained without requiring the user's hands to pass close to the needle tip, and therefore allowing a quite safe operation. The disclosed device, while affording the required safety, has, however, a rather complex structure and is, accordingly, quite expensive. In particular two additional elements are required, i.e. the protective sheath and the tubular needle guard, whose construction is particularly complicate.
The object of the present invention is therefore to provide a one-way intravenous catheter which allows the same safety and ease of operation as the catheter of the prior art, while being of a simpler construction and involving lower production costs. It is evident that, in order to result in a real contribution to the safety against blood borne diseases, a device of the kind disclosed must be reasonably cheap, so as to be available to a wide market.